docs: def std(self):
          """
          The standard deviation of the best results of each trial.
  
          Returns:
              float: standard deviation of measured seconds
  
          Note:
              As mentioned in the timeit source code, the standard deviation is
              not often useful. Typically the minimum value is most informative.
  
          Example:
              >>> import math
              >>> self = Timerit(num=10, verbose=1)
              >>> self.call(math.factorial, 50)
              >>> assert self.std() >= 0
          """
          import math
          chunk_iter = chunks(self.times, self.bestof)
          times = list(map(min, chunk_iter))
          mean = sum(times) / len(times)
          std = math.sqrt(sum((t - mean) ** 2 for t in times) / len(times))
          return std